Scientists from the University of Waikato and University of Canterbury and researchers from the Korean Polar Research Institute returned recently from seven days of diving under Antarctica’s sea and lake ice in the Ross Sea.
The research data they were collecting is to help monitor the impacts of climate change on the environment and carried out between November 7th to December 2nd last year at Jang Bogo Station at Terra Nova Bay, and Cape Evans.
Diving in these extreme conditions means unusual hazards. Dives are through holes in two metre thick ice at -2 degrees. But the water is very clear, with low current, low irradiance, and with the sea or lake floor is typically visible from the surface. So dives follow a well-rehearsed Dive Plan.
Single and paired divers operate down these holes on lifelines beneath a dive locker facility in a hut erected over them.
All divers had significant previous experience – Dive Supervisor, Waikato University’s Professor Ian Hawes, has been diving in the Antarctica for 40 years – and they adhere to strict protocols and procedures. The diving is also part of the science programme.
The goal of the research programme, reports Science Diver and Waikato University Senior Technician Warrick Powrie, was to collect data to assist in detecting long term changes in the marine ecosystem linked to climate change.
“For the work we used remote video processes, with divers describing the biological communities on the seafloor, he said. “The monitoring scheme supplements and tests our models of how the marine ecosystem will respond to anticipated environmental changes.”
Along with the Korean programme, our long term research programme is on the dynamics of inshore marine ecosystems in the Ross Sea against which the effects of anticipated climate change-induced change can be measured, he said.
To do this they deployed logging sensors at Terra Nova Bay and Cape Evans, and assessed the status of benthic communities using video transects and 3D modelling of transect lines.
Warrick said his role was as dive tender and safety person was to make sure the diving operations ran smoothly and safely while divers are in the water. “Safety is paramount,” he said.
Rigorous safety protocols highlight risk
The Dive Plan strictly adhered to in Antarctica follows protocols that have been developed over many years and includes:
- Every diver in the water has two attendants, one standby diver, and a record keeper.
- All gear is tested before the divers undertake a maximum of two dives a day, to a maximum depth of 30 metres, and with no diver doing more than five consecutive dive days.
- Identifying the nearest recompression chamber (in this case McMurdo Hospital) with an evacuation plan linked to the communication systems at Scott Base via an Iridium phone or high frequency link.
- Hypothermia risk is minimised by on site heated accommodation with a feeding facility where divers and standby divers can take refuge and change after diving. Suit leak results in dive termination.
- Dive holes about 50 metres from the primary dive hole must all be uncovered and chipped free of ice at the start of every day’s diving.
- Equipment has to be high quality with full redundancy of gas supply, dive tethers, 15 litre steel faber cylinders, with hang tanks at 6 metres, and near the bottom of the hole.
- Cold water temperatures can lead to a regulator’s first stage freezing open, hence a backup regulator must be available.
- To minimise the risk of decompression sickness all dives are planned conservatively to a depth of 30m. Dives are all planned as square dives, using tables with conservative profiles and slow ascents and a safety stop for two minutes at 5m. Air reserves are set at 70 Bar with two 8 litre steel tanks suspended at working depth and at 6m. Cylinders are fitted with twin pillar valves to allow two fully independent first and second stages.
- Divers are tethered.
- Potential dive hole sites are checked by drop camera prior to making a dive hole to ensure excessive accumulation of platelets below the ice is not present to avoid the risk of Brash ice.
- Since the air pressure at sea level in Antarctica is chronically low – it can sometimes equate to 300m above sea level – the dive team has to equilibriate to the ambient pressure. Diving is always conservative and to Bhulman or Us Navy tables and guidelines.